The present invention relates generally to radomes, and, more particularly, to compensated radomes for eliminating bore sight errors produced by refraction of the radome.
Optically-transparent radomes suffer from refraction, due to the bending of light through the radome material. It is desired to compensate such radome effects that degrade performance of present-day missile radar seekers. These radome-induced distortions ultimately limit the missile""s ability to detect stressing targets in the presence of severe interference. RF adaptive array processing places very stringent requirements on antenna calibration and radome compensation. These requirements will only increase in the future, as inexpensive countermeasures become increasingly sophisticated and widespread.
Compensating bore sight shift is typically accomplished by measuring the radome bore sight shift in a RF chamber and storing compensation coefficients to be used in software algorithms. Compensation coefficient tables are typically a function of RF and gimbal angle, both azimuth and elevation. System requirements drive compensation accuracy, which in turn drives the quantity and quality of data that must be measured and stored for compensation. Heating caused by aerodynamics, radome-to-radome variability, and aging may also have to be considered when compensating. Such compensating methods add to the cost and complexity of radome systems
Thus, there is a need for compensated radomes that avoids most, if not all, of the foregoing problems.
In accordance with the present invention, a compensated radome is provided, comprising an inner layer of a negative index of refraction material, often referred to as a xe2x80x9cmetamaterialxe2x80x9d, and an outer layer of a positive index of refraction material. The thickness of the two materials and their respective refractive indices are adjusted so that a beam of light passing through the radome is effectively not refracted.
The metamaterial-compensated radomes of the present invention solve the bore sight angle problem with a minimum of complexity.